A cotton straw chopping and returning device is designed for the small field in south of China, which consists of cutting part, standing stem part, stubble chopping part, etc. cotton straws were feed by standing stem part, and then cut from top to bottom in turn as well as stubble chopping. The device was mounted to the trolley in the soil bin and test by single factor experiment and regression orthogonal experiment. The qualified rate of cotton cutting length, power consumption and stubble rate are influenced by the moving speed, sawing disk rotational speed and guide slit width. It is shown that the moving speed, saw disk rotational speed and guide slit width have a successive effect on the qualified rate of cotton cutting length and stubble rate. Whereas the power consumption was mainly effected in turn by the saw disk rotational speed, the moving speed and guide slit width. The operation parameters were optimized by plan solution. When the device was working under the sawing disk rotational speed of 860 r/min, moving speed of 0.65 m/s and guide slit width of 60 mm, the lowest power consumption was achieved to 5.91 kW with the qualified rate of 85% and stubble rate of 90%.